The use of implantable fluid medication dispensers is presently well known in the art. Examples of implantable fluid medication dispensers are contained within U.S. Pat. Nos. 5,328,460, 5,443,450 and 5,643,207. Such dispensers are used to dispense a specified amount of medication into a patient's body, and may, for example, deliver low doses of morphine into a patient's body to treat cancer pain.
Implantable fluid medication dispensers typically include an internal fluid medication reservoir for receiving, storing and dispensing a supply of a fluid medication. Such a reservoir is generally included within a housing of some shape or form that may be implanted in the body. Other components of such a device include a power source (such as a battery), a mechanism for pumping the fluid medication into the patient's body, and a programmable mechanism to assist in dispensing the fluid medication according to a predetermined schedule.
Because those fluid medication dispensers are implanted within a patient's body, they must in general be periodically replenished with medication. As a result, implantable fluid medication dispensers may include some means to replenish the fluid medication within the reservoir. U.S. Pat. No. 5,443,450 to Kratoska et al. discloses a typical reservoir refill assembly. Unfortunately, determining the level of medication contained within a fluid medication dispenser has proved to be problematic. At present, the absence of a fluid medication being dispensed to a patient is generally detected by physiological measures. Such measures may include symptoms associated with the malady to which the fluid medication is directed to prevent or abate.
There exists, therefore, a significant need for improvement in the measuring abilities of such implantable medication dispensers. Instead of relying upon symptomatic factors to determine when an implantable fluid medication device is in need of a replenishment of fluid which may cause unwarranted pain to the patient, it would be desirable to provide a means to determine the amount of fluid remaining in another more efficacious manner. The present invention fulfills at least some of these needs and provides further advantages.
Disclosures relating to implantable medication dispensers include the U.S. Patents listed below in Table 1.
TABLE 1 Prior Art, U.S. patents. 5,328,460 July, 1994 Lord, et al. 5,443,450 August, 1995 Kratoska, et al. 5,643,207 July, 1997 Rise
As those of ordinary skill in the art will appreciate readily upon reading the Summary of the Invention, Detailed Description of the Preferred Embodiments and Claims set forth below, at least some of the devices and methods disclosed in the patents contained within Table 1 may be modified advantageously by using the teachings of the present invention.